Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G49/00—Compounds of iron
  • C01G49/02—Oxides; Hydroxides
  • C01G49/06—Ferric oxide [Fe2O3]
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G49/00—Compounds of iron
  • C01G49/02—Oxides; Hydroxides
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S423/00—Chemistry of inorganic compounds
  • Y10S423/01—Waste acid containing iron
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S423/00—Chemistry of inorganic compounds
  • Y10S423/01—Waste acid containing iron
  • Y10S423/02—Sulfuric acid

Definitions

• the invention relates to a method for the preparation of iron hydroxide, iron oxyhydrate or iron oxide from filter salts of dilute acid recovery.
• Dilute acid consists essentially of dilute sulfuric acid which contains the dissolved salts (mainly iron salts).
• the latter is concentrated and filter salts, or green salts, are produced, which are separated.
• the filter salts are thus produced in large amounts and, on account of their accompanying components they cannot easily be used industrially, but have to be disposed of, often at great expense.
• the invention is addressed to the problem of overcoming the disadvantages of the state of the art and especially to create a process whereby iron hydroxide or iron oxide with a content of >90 wt.-% of Fe 2 O 3 can be recovered from the filter salts of dilute acid recovery.
• the problem is solved by a method for the preparation of iron oxide, iron oxide hydrate or iron oxide for filter salts of dilute acid recovery wherein the filter salts are dissolved in water, the solution is adjusted to a pH of ⁇ 1, preferably ⁇ 0.5, then by adding a strong base with stirring a pH of 2 to 4, preferably 3 to 3.8, the substances then precipitating are separated in a known manner, the remaining solution is adjusted with the addition of a strong base and/or an oxidizing agent to a pH of 6 to 8, the precipitating iron hydroxide or iron oxide hydrate is separated from the solution, washed, dried and if necessary dried and/or calcined to iron oxide.
• the filter salt solution already has a pH of ⁇ 1 and then does not have to be adjusted separately. Otherwise, sulfuric acid or dilute acid is used for the adjustment of the pH.
• the filter salt solution contains preferably 200 to 350 g of solid matter per kg of solution.
• An alkali metal hydroxide solution is used preferably as the strong base; caustic soda solution or caustic potash solution is especially preferred.
• the substances precipitating at a pH of 2 to 4 contain mainly metatitanic acid. Preferably, this is fed back into the titanium dioxide process.
• Air, oxygen or hydrogen peroxide (H 2 O 2 ) is used preferably as oxidant. When air or oxygen are used they are blown into the solution.
• the calcining or drying temperature amounts preferably to 200 to 1300° C., especially preferably 300 to 1300° C., and quite especially preferably 600 to 1200° C.
• the calcining or drying can also be performed under vacuum.
• the advantage of the method of the invention is that high-quality iron hydroxide or iron oxide hydrate and, after calcining, iron oxide with a content of >90 wt-% Fe 2 O 3 is obtained.
• the washing of the precipitated iron hydroxide is preferably repeated until the electrical conductivity in the washing filtrate is under 200 ⁇ S/cm ⁇ 1 especially preferably under 150 ⁇ S/cm ⁇ 1 In this manner an iron oxide is obtained after calcining, with a content of 94 wt-% Fe 2 O 3 .
• an aqueous filter salt solution was prepared. This solution had a pH of 0. This means that sufficient acid was adhering to the filter salts, so that a separate addition of acid was unnecessary.
• the temperature of the solution was about 23° C.
• the solution was adjusted by stirring with about 150 ml of 50% caustic soda solution to a pH of 3.5, the temperature of the solution increasing to 55° C. After a 2-hour maturation phase at about 40° C. the precipitated solids were separated from the filtrate with a suction filter. The filtrate cooled during the solid-liquid separation to about 25° C.
• the filter solution was then again adjusted with 180 ml of 50% NaOH, with turbulent stirring during which atmospheric oxygen went into the solution, to a pH of 7.8, when much iron hydroxide precipitated.
• the iron hydroxide was dried in the dryer for 12 hours and then calcined for 2 hours at 600° C. in a laboratory oven in atmospheric air.
• the iron oxide obtained had a content of 94.5% Fe 2 O 3 .

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Compounds Of Iron (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=29761981

Family Applications (1)

Country Status (4)

Cited By (2)

Families Citing this family (4)

Citations (7)

Family Cites Families (7)

• 2002
  • 2002-07-16 DE DE10232069A patent/DE10232069A1/de not_active Withdrawn
• 2003
  • 2003-07-08 US US10/745,693 patent/US7144561B2/en not_active Expired - Fee Related
  • 2003-07-09 EP EP03015714A patent/EP1382571B1/de not_active Expired - Lifetime
  • 2003-07-09 DE DE50302037T patent/DE50302037D1/de not_active Expired - Lifetime
  • 2003-07-14 JP JP2003196654A patent/JP2004051477A/ja not_active Ceased

Patent Citations (7)

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